It’s a one-page reference table. Every subnet mask from /8 to /32 sits next to its
wildcard mask, block size, and usable host count, in decimal and in binary. Print it
in A4 or US Letter and keep it by your keyboard for the CCNA exam or for the job.
Is it a free download? Yes. Drop your email below and it lands in your inbox. No
payment.
What this PDF is
A subnetting cheat sheet only works if you can find the row you need in about two
seconds. This one’s built for that: one CIDR table, /8 through /32, decimal and binary
side by side, so you’re not translating 255.255.255.192 into 11111111.11111111.11111111.11000000
in your head during a timed exam.
Here’s the mistake that costs people more marks than the math itself. A /26 gives you
64 addresses total, not 62. The network address and the broadcast address are still
addresses, they’re just not usable ones. Miss that distinction and you’ll misread a
question that asks for “addresses” instead of “usable hosts.” That’s why this sheet
keeps total addresses and usable hosts as two separate columns instead of one, so the
gap is visible instead of memorized.
What’s inside
- Full CIDR table, /8 to /32: subnet mask, wildcard mask, block size, total
addresses, and usable hosts for every prefix, decimal and binary - Binary column: the actual 1s and 0s behind each mask, next to the decimal
shortcut, so you can check your work either way - Powers-of-2 reference: host bits mapped straight to usable hosts, in both
directions, no calculator needed - IPv4 classes and private ranges: Class A through E, plus the three private
ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and the loopback block - IPv6 prefix quick-reference: the /48, /56, and /64 prefixes you’ll actually run
into on the exam and on the job - Subnetting shortcuts, one page: the magic-number method, the wildcard-mask
shortcut, the broadcast-address formula, and the /30-for-point-to-point rule - Printable, A4 and US Letter: built to print single-sided and sit next to your
keyboard, not just live in a browser tab
Who it’s for
- CCNA 200-301 candidates who want the subnetting math automatic before exam day,
not worked out from scratch each time - Junior network engineers who want a ten-second lookup instead of opening a subnet
calculator for every VLAN - Readers of our Subnetting Explained
guide who want the tables from that article on paper - Anyone doing VLSM practice who needs block size and host count in the same place
It’s a lookup table, not a lesson. If you haven’t seen why the block-size method works
yet, start with Subnetting Explained.
This sheet is what you keep open once you already get it.
Print format
Two sizes in the same download: A4 for everywhere outside North America, US Letter for
inside it. Both are one page per side, so it prints clean on a single sheet, front and
back, no scaling issues at the printer.
